I don't understand people who criticize the ending of the movie so vehemently. Bertino has made a really different thriller. Everyone finds the 'Because you were at home' response silly or at least ill-conceived.
But let me point out, the movie was based on REAL events from 3 years ago, the beginning of the movie gives details of who was killed, when was killed and how many of these types of violent crimes take place every year, the only open question left is 'why'? The audience already knows how the case will turn out, yet the poignancy of the movie is by no means lost. This is certainly a credit to the directors and the entire cast.
The killers' answer to the victims' questions 'why?' is shocking, because it is through it that the director reveals the whole essence of these killers - they are people who just like to torture and kill people for no reason, who enjoy other people's fears and pain, they are simply sick people. And bravo to the director who so successfully managed to paint this image of REAL homicidal maniacs.
This is not 'Saw' or 'The Silence of the Lambs', certainly great movies, with villains as iconic for cinematogrophy, as REAL.
Of course the final scene (on the road) and the dialog itself I thought was just brilliant. I won't recount it here, but it is this scene, together with the response of the killers, which caused many people to be perplexed, it is all of this together that makes the viewer truly horrified....